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Including Group 14 and 15 Modes of Action in Weed Management Programs

Eric Johnson, Brian Beres and Chris Willenborg

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Group 14 (ppo) herbicides• Inhibit Protoporphyrinogen oxidase enzyme

• Leads to formation of singlet oxygen (free radicals that peroxidase lipids in cell membranes)

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Group 14 Symptoms• Effected plants initially have a “watersoaked” appearance,

followed by rapid wilting and “burning,” or leaf speckling and browning. Plant death occurs within a few days.

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Group 14 Foliar Applied Herbicides

Chemical Trade Name

Soil

Residual

Half-Life

(Days)

Pyraflufen-ethyl Goldwing (+MCPA),

Blackhawk (+2,4-D)

None <1day

Carfentrazone CleanStart,

Conquer

(+Bromoxynil)

None 1.5

Saflufenacil Heat, Sharpen Short-term

(2-3 weeks)

15-28

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Group 14 Soil Applied Herbicides

Chemical Trade Name

Soil

Residual

Half-Life

(days)

Flumioxazin Valtera, Chateau ~ 4 weeks 12-18

Sulfentrazone Authority

Authority Charge (+ Carfentrazone)

Season

long

21-111**

** From studies on Saskatchewan soils by Szmigielski et al.

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Pyraflufen-Ethyl• Fast acting

• Appears to be synergism between foliar Group 14’s and phenoxy herbicides

• BlackHawk (+2,4-D ester)

• Pre-seed wheat (spring, durum, winter), barley, rye

• Soybean – 7 days prior to seeding

• Chemfallow

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Pyraflufen-Ethyl• Goldwing (+ MCPA ester)

• Pre-seed field pea

• Pre-seed wheat (spring, durum, winter), barley, rye, oats, triticale, canary seed, corn (field, sweet)

• Flax and other pulses to be added to label this year

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Conquer (bromoxynil + carfentrazone)

• 2 modes of action

• Can be applied prior to canola

• Improved control of volunteer canola than carfentrazone alone.

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Flumioxazin (Valtera, Chateau)• Fall / spring

• Soybean, Field pea, chickpea

• Wheat – 7 days prior to seeding

• Potatoes

• Apply after hilling

• Fall applied prior to lentil registration being pursued

www.usask.caNumbers above bars indicate # of site-years

23 4

Fall applied Valterra – Weed Control Saskatoon and Scott, 2014-15

23 4

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• Valtera effective dry bean desiccant but how about lentils?

• 3-year study at Scott and Saskatoon investigated glyphosate, pyraflufen-ethyl, flumioxazin, saflufenacil, glufosinate, and diquat.

• Ranking: glufosinate = diquat > saflufenacil > flumioxazin > pyraflufen.

• Addition of glyphosate to saflufenacil, flumioxazin+ pyraflufen improved desiccation compared to either product applied alone.

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Sulfentrazone (Authority, Authority Charge)

• Requires some soil moisture, but highly effective on kochia, redroot pigweed, cleavers, and lambsquarters.

• Activity increases as soil pH increases; no need to use high rate in southern Alberta.

Source: Jenks, NDSU

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Group 15 Soil Applied HerbicidesInhibitors of Very Long Chain Fatty Acids

Chemical Trade Name Registered on:

Pyroxasulfone Focus (+ carfentrazone) Wheat (spring, winter, not

durum), soybean, corn

Dimethanamid-P Frontier Max Corn, dry beans

S-metolachlor Dual II Magnum Corn, soybeans, dry beans,

potatoes, soybean, lupins

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Biosynthetic pathway of VLCFAs in plants.

Source: Yoshitaka Tanetani , Koichiro Kaku , Kiyoshi

Kawai , Tomonori Fujioka , Tsutomu Shimizu

Pesticide Biochemistry and Physiology Volume 95,

Issue 1 2009 47 - 55

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Group 15 – Focus (pyroxasulfone)

• Do not affect seed germination but have a potent effect on shoot formation in the emerging seedling.

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• Weeds fail to emerge

• If emerged, monocots appear twisted and malformed / crinkled

Pyroxasulfone symptoms

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• Broadleaf seedlings that emerge

• Cupping, crinkling

• Shortened leaf midribs produce a drawstring effect on leaf tip.

Pyroxasulfone symptoms

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Pyroxasulfone – emerged grass weeds may have damaged root system

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Japanese Brome Control – Studies in winter wheat: Coalhurst,

Lethbridge, AB; Scott, SK. 2011-2013: 9 site-years.%

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all

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pr.

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12

Focus 1

50

Fie

rce

www.usask.ca

Downy Brome Control in Winter Wheat; 9 site-years%

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all

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Focus 1

12

Focus 1

50

Fie

rce

www.usask.ca

Downy Brome Biomassg m

-2

Error bar = LSD0.05

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www.usask.ca

• Research underway on lentils

• Some growers experienced lentil injury in southern SK where they received excess spring rain.

Focus

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QUESTIONS ??